Piston and the method of producing same



Nov. 13, 1928. 1,691,450

H. A. SOULIS ET AL PISTON AND THE METHOD OF PRODUCING SAME Filed Aug. 9, 1924 I N VEN T2312. Hamid/1. Sou/{s a Wilbur Z 5011115 ATTORNEY.

Patented Nov. 13, 1928.

UNITED STATES PATENT OFFICE.

HAROLD A. SOULIS AND 'WILBUR '1. SOULIS, OF NEW YORK, N. Y.

' PISTON AND THE METHOD OF PRODUCING SAME.

Application filed August" 9,- 1924. Serial No. 731,032.

The present invention relates generally to improvements in internal combustion engines, and is more particularly directed to pistons therefor and the'method ofi'producing the same.

As is well known, many attempts have been made to overcome the well known "disadvantages which are inherent to cast-ironpistons, as generally employed in internal combustion engines. For example, pistons have been made from steel and aluminum alloys of dif ferent compositions in a'n'efiort to lessen vibration, increase acceleration, and produce greater power for a given fuel consumption. However, pistons of these typeshave been more or less unsuccessful from a practical and commercial standpoint, largely by reason of the fact that the steel or the aluminum alloy piston does not possess the same coefficient of expansion as the wall of the engine cylinder, which obviously results in poor engine performance under varying loads and conditions of operation.

The general object of thepresent invention is to increase the eficienc of internal combustion engines by provi ing a light-weight piston of high thermalconductivitg therefor, whereby vibration will be su stantially eliminated and .greater flexibility of operation obtained with a relative increase in power and speed for a given consumption of fuel.

More specifically, the object of this invention is to provide a piston for internal combastion engines and a method of constructing same whereby thegeneral objects, above set forth, may be attained.

It is a further object of this invention to provide a piston for internal combustion engines by the practicin of our method of construction, which is ormed or built 1 1p of metals possessing different characteristics, such, for instance, as a ferrous metal and an aluminum or aluminum alloy, wherein the advantages residing in theuse of ferrous metal or aluminum or an aluminum alloy may be utilized for the production of a composite structure possessing qualit1es which could not be obtained by the use of one or'the other separately.

Our invention also contemplates a piston, as heretofore described, in whichtne parts formed of ferrous metal and an alum num alloy are so united that a structure Wlll be provided which will ossess all'of the advantages of a cast piston 1n resisting the strains and stresses to which it is subjected in eqfiiivalents, both in structure and uses, to w ich we may be entitled under our invention in its broadest aspect.

.We shall now proceed to describe our invention with reference to the accompanying drawings, wherein a preferred embodiment of a piston is illustrated for the purposeof presenting a clear and comprehensive disclosure, it being obvious that pistons of other forms may be produced in accordance with our method without ,departing from the spirit and scope of our invention.

In the drawings Fig. 1 is a view in elevation, partly in section,of a piston made in accordance with our invention.

' Fig. 2 is a bottom plan view of the structure shown'in Fig. 1; and

Fig. 3 is a fragmentary detail, in elevation, of the-skirt prior to the association of the head and cooperating parts therewith.

Referring now'to the drawings in detail, in which like characters of reference are emplo ed to designate similar parts in the severa views, 7 indicates the skirt of the iston, which is of a cylindrical or tubular con guration and is formed, b casting, or otherwise, of ferrous metal, suc for instance, as gray iron. 1

As will be observed, thewall of the skirt is provided with diametrically opposite wrist pin openings 14, the u per or head end there- I end 8 may be preserved.

-An inwardly directed flange 10 surrounds the top of the head or u per portion of the skirt 7 while a similarly. isposed flange 11 is provided at the bottom of said skirt for reinforcement purposes, The shoulder 11 produced by the formation of the head 8 of the skirt 7, as described, is preferably undercut at 12, and provided with equidistantly spaced openings 13 of any suitable form, the purposes of which will be hereinafter apparent.

The piston head indicated at 15 which is slightly less in diameter than the body of the skirt is of aluminum or an aluminum alloy, or other suitable metal and is provided with the usual piston or packing ring grooves 16 formed on the periphery thereof. The wrist pin bosses 17 are integral with the head 15, as will be clearly evident from Fig. 1 of the drawings, and are connected by the web 18,

. which also serves as a reinforcement for the head (see Figs. 1 and 2). p

In the production of a piston in accordance with our invention, the skirt 7 preferably cast in grey iron, which will run in thin sections, is inserted in a mold of the proper dimensions with a suitable core in place. The molten metal in which the head is to be formed is then poured through the gate of the mold. Obviously, this molten metal will flow through the slots 9 and openings 13 in the skirt 7, and upon cooling will contract, so that the head of the piston will be positively and tightly bound or interlocked to both the inner and outer surfaces of the ad 'acent portion of the skirt. In fact, it has een found that the metal of the head enters the pores of the skirt metal so as to produce a partial amalgamation of the two, particularly if the sur aces of the upper or head portion of the. skirt are rough. It will, of course, be understood that a piston may be produced in accordance with our invention by means of a metal die, as well as through the medium of a sand mold as just described.

The wrist pin bosses 17 may then be drilled to provide a bore 17" for the wrist pin, the outer end of each of said bosses, as will be noted from Fig. 1 of the drawings, being disposed within and united to the metal forming the cooperating opening 14 of the skirt 7. Following this operation, the piston may be machined in the same manner as a cast iron or cast aluminum piston, suitable oil holes (not shown) being provided in the skirt as desired.

From the foregoing, it will be evidentthat a piston made in accordance with our invention, will possess the desirable characteris tics of allaluminum and all cast iron structures, without the disadvantages of either. A piston embodying our invention weighs considerablyless than one of the same length and diameter in cast iron. The high thermal conductivity of the head metal meets the requirements of increased compression ratios, as in engines of resent designs, while the skirt with its coe cient of expansion corresponding to that of the cylinder wall, pro- .the bearing surfaces.

vides for close tolerances in fitting and insures the elimination of the objectionable slap of the various aluminum alloy structures, with a maximum reduction of wear on Another factor, in adding to the durability of the structure, resides in the formation of the wrist-pin bosses integral with the head, thereby relieving the skirt of the detrimental loads, especially those of the firing stroke, and permitting of the use of a skirt wall of an extremely thin section, with the obvious advantages.

The provision of the shoulder 11, or other circumferential or suitable reinforcement for the wall of the skirt, preferably in the zone to which the expansion forces of the head metal are communicated, renders the use of cast iron as the skirt metal practical in the production of a light weight composite piston. \Vithout. such reinforcement, which effectively resists the more rapid expansion of the head metal and results in a substantially uniform rate of expansion of the entire structure, the thin wall section which is necessary to obtain the advantages which flow from a light weight piston and which are essential to a successful aluminum alloy and cast iron structure, could not be utilized, it being manifest that the relatively small areaof the wall of the skirt which is thicker in section than the remainder thereof, for reinforcement purposes, does not noticeably add to the weight of the skirt or the structure, as a whole. In other words, by providing the skirt wall with .a reinforced area, the expansion of the head metal is confined within the elastic limits of the cast iron, so that the unequal rates of expansion of the two unlike metals does not preclude the use of the light-weight thin-walled skirt, as, otherwise, would be the case. Thus, with the skirt embedded within the head structure and united thereto as described, a composite piston is produced which is capable of successfully resisting the rending forces developed by unequal expansion in the two metals of the piston, as wellas those detrimental forces which are transmitted thereto in operation.

While we have described a specific form of piston and the method of producing the same, it will be evident that by practicing our method of manufacture, a piston of any desired configuration or composition may be produced; also that to meet different requirements, changes in the layout and arrangement of'the' cooperating elements may be made. For example, the interlocking openings, such as the slots 9 and the holes 13, may be located otherwise than shown and .of any suitable configuration; also, the shell or skirt may be of aluminum and bronze or any other suitable combination of metals which may be suitable while in lieu of aluminum or an aluminum alloy a head of bronze or coppermay be III neonate joined to the iron skirt, without departing from the spirit and scope of our invention.

What we claim is: i

l. A 'piston for internal combustion engines, comprising a tubular shell of cast iron, the wall thereof adjacent one end being inset by the formation of an integral circumferential shoulder having a grooved top sur face and provided with spaced openings inwardly inclined from said groove, the inset portion of said shell wall being formed with rows of staggered elongated openings, and a head of an aluminum alloy with integral wrist pin bosses cooperating with wrist pin openings oppositely located in said shell, united thereto; said head metal being disposed within the groove and perforations of said shoulder and the elongated openings in said wall thereabove, and on each. side of the wall of the shell above said wrist pin openings, whereby said head and said shell are permanently interlocked.

2. A piston for internal combustion engines comprising a tubular shell of cast iron having an inturned flange at each end, the

wall of said shell adjacent one end being inset by the formation of a circumferential shoulder having a grooved top surface and provided with spaced apertures, the inset portion of said wall being formed with a series of rows of elongated openings in staggered relation, and a headof an aluminum alloy, with integral wrist pin bearing-bosses interlocked with oppositely located wrist pin openings in the wall of said shell below said shoulder, the inset portion of said shell and said shoulder being completely embedded within the head metal, the; resultant disposition of the head metal within the openings of said shoulder and said inset portion of the shell providing a positive interlocking of said head and said shell longitudinally and radially of the piston.

3. A piston for internal combustion engines, comprising a shell of cast iron having oppositely located annular wrist-pin openings in the wall thereof, that portion of the wall above said openings being inset by the formation of an inwardly disposed circumi ferential shoulder, an inwardly directed circumferential flange at the upper end of said shell, a head of an aluminum alloy, embodydependent wrist-pin bossesand a diametrically disposed rib connecting said i bosses to the interior of said head, cast upon said shell and means for mechanically uniting said head metal and said shell to resist rending longitudinal and radial forces, said means including spaced apertures in said shoulder and rows of staggered peripheral openings in the shell above said shoulder, within which the head-forming metal produces interlocking surfaces connecting the inner and outer portions thereof, the contiguous wall of the shell being completely embedded within the head metal and united thereto by fusion, v

4. A. piston for internal combustion engines comprising a cast iron cylindrical shell, the upper end of which is of a reduced diameter and provided with circumferential openings, the wall of said shell abutting upon the portions of major and minor diameters being of a greater thickness than that of the and a head of an remainder of said wall aluminum alloy cast upon the shell, the head metal being interlocked with said shell the wallthereof, the upper end of said wallbei'ng inset and provided with'circumferential openings, said inset being connected to the remainder of the shell by a ledge having a greater thickness than the wall of the shell above and below said ledge and a head of an aluminum alloy having integral wrist pin bosses cast upon said shell, the head metal extending through said circumferential openings and making contact with the inner and outer surfaces of the wall of said shell adjacentits upper end and with said ledge.

6. A piston having a cast iron shell with an aluminum alloy head and integral wrist pin bosses cast on said shell in interlocking engagement with the inner and outer surfaces of the wallthereof, the major portion of the wall being of a substantially uniform thickness and of a tensile strength incapable of withstanding the expansion forces of the head metal, a portion of said wall in the zone of contact between the harder and softer metals being reinforced to counteract the detrimental forces transmitted thereto by the radial expansion of the head metal.

7 A light weight composite piston for internal combustion engines, comprising a shell ofcast iron, apertured to receive a wrist pin, having arelatively thin wall reinforced in a zone. between-the wrist pin apertures and theupper end of the shell and a head of an aluminum alloy with integral wrist pin bossescast upon said shell in engagement with th'elinner and outer walls thereof, the detrimental expansion forces of the head metal transmitted to said shell being counteracted in the aforesaid reinforced zone of the shell; A I

8. A; light weight composite piston for internal combustion engines embodying a shell of cast iron, apertured to receive a wrist pin, having a relatively thin wall of a tensile strength incapable of withstanding the dotrimental forces exerted thereon by the expansion of a metal having a greater co-efiicient of expansion than the shellmetal, said Wall being provided with an integrzllly formed reinforcement of a tensile strength suflicient to counteract the aforesaid detrimental forces, and a head of an aluminum alloy cast upon said shell in contact with the inner and outer surfaces of the wall thereof in the region of its greatest tensile strength.

9. A piston for internal combustion engines, embodying a shell of cast iron apertured to receive a wrist pin and formed with an internal ledge at its lower end, the wall of said shell above said ledge being substantially of a uniform thickness with an integrally formed reinforcement adjacent the upper end of the shell and a head of an aluminum alloy with integral wrist pin'bosses cast upon the upper end of the shell in contact with the inner and outer surfaces of the wall thereof, said reinforcement resisting the detrimentalforces transmitted to the shell by the unequal expansion of the shell and head metals.

HAROLD A. SOULIS. WILBUR-T; SOULIS. 

